Technical Who has the capability of narrowing connecting rods?

Anyone know of a machine shop that narrows connecting rods? It may make or break my 390 Caddy build.
I am waiting on the manufacturer to call me back to see if this is even safe enough to do.

Thanks

Root

 

How much are you removing? Seems like a good job for a surface grinder. Or maybe the manufacturer will do it.

 

Rough calculation is .117”. Wanting to use a Pontiac 455 rod in my 390 Cadillac.

 

My machine shop would just make new ones out of aluminum. Whatever spec you need.

 

Do you need the whole rod narrowed or just the crank journal end? We used a lathe to narrow 348 Chevy rods to use in a Ford 351 W stroker after the crank was offset ground. Any machine shop with a magnetic table surface grinder can probably do them too.

 

???
Is this for a typical I-beam cross section rod?
Do you just need to clear one point on the crank rotation?
If so, any chance of a small relief notch in the bottom of the bore?

I'd be nervous doing anything to weaken or change the profile of rods in general.

 

The problem is that no one reproduces a rod for the Caddy. The original caddy rod was 6.5" with a .8775 cap width. The new rod is 6.650 and the cap width is .990. The rest is the same. I would love to find someone local, so I can set my side gap. Just wanna make sure that I can use them prior to dropping the coin.

Oh and it is an H beam rod.

 

Also the chamfers on both sides need to be re cut..... After you cut or grind a equal amount of stock on both sides of the rod.....

 

I do it in the Bridgeport. They don't have to be perfect, just not too tight. It's just side clearance.

 

Sorta what Hemi Joel said...except -
Too lose will not only cause excessive movement and bearing wear, it will also case excessive oil escape and cause low oil pressure.
As long as the cuter or grind wheel doesn't dig into the main part of the rod body. You need enough "shoulder" for things to be able t"pass" each other with no contact.
Watch the centering of the rod within the piston also. A small offset is ok, just don't get carried away.

Mike

 

If you are just looking for a set of rods there is a set on Ebay for $100.

 

I agree with all that Mike says there. What I mean by not perfect is somewhere in the .012 - .018 range for a performance build, and parallel within a thou or so. In other words, close enuff for a bridgeport to handle with careful set up. I have seen plenty of mopars with chevy rods end up with .035 side clearance, with apparently no ill effect. Oil shedding will then be limited by the rod bearing to crank clearance. So to dredge up an old engine builder axiom: if the clearance is loose, you will know. If it's tight, everybody will know.

 

I thought Kanter and Caddy Daddy sold them.

 

If they do make them, I’ll go that way. I just don’t know the history on my rods. Who knows how many hours/cycles they have on them.

 

Wow they do make them.
77.25 each! Works out to about $618 set.
https://www.kanter.com/productdetai...&CategoryID=32&ProductCode=355&Router=Gallery
The aftermarket H beams are cheaper.

 

That's a good price . I just paid about that much for a set of small block Ford rods made by Crower.

 

Yeah, but those are good rods. That price was for plain old stock rods.
Here's the ones I was looking at.
http://www.jegs.com/i/Scat/942/66625/10002/-1

 

Call Jim Butler Racing, if it has to do with Pontiac's, he will know how to make them work.
http://jbp-pontiac.com

 

Sounds like you just need to check out your caddy rods. Piston pin/bearing fit. Put 2 rods on 1 pin & check for parallel. Big end size & possible out of round (which is typical). Then get a second opinion from your machine shop. They can mag them too. New bolts are nice.

Here's what's wrong with your Pontiac idea. According to your measurements, Pontiac rods are .150" longer. That means that you will need pistons with a .150" shorter compression height (pin closer to top of piston by that much).
Unless those pistons are shelf items, you will be shocked at how much specials cost! Another problem with longer rods is that you will loose some low end grunt but at 400 cubes it probably wouldn't be noticeable.

But I don't know nuthin' about caddys or Pontiacs. There might be some good secrets out there. I'm just speaking from general engine building knowledge.

Mark





sent from the red phone

 

Call CROWER It's free to talk.....
https://www.crower.com/

 

Squintboy. that's funny you say longer rods used to hurt the bottom end. That's exactly what we did to help our dirt cars up off the corner's . We would use 6 inch Olds rods in our small block Chevy's. The tech man had to pull the motor all the way down to find them.
Roothawg , mag your rods for cracks, polish the beams. Change the bolts out unless you are running a blower with a ton of boost , you should be fine. We had to run stock rods in our dirt late models and we did just that, and turned the motors 7,000 twice a lap for 50 - to 100 laps depending on what they were running. Would run a whole season that way. Never broke a rod.
Custom pistons run about $ 850.00 per set from Diamond.

 

It could be done on a CNC lathe with enough swing. And do the chamfers at the same time. 2 operations.

 

I will have to see if they even have rod bolts available. I was planning on having Venolia build me a set of pistons anyway.

No forged stuff available for rebuilds. Only cast. So, that's why I just figured I would suck it up and pay the piper.

The pin height is pretty far down anyway. It's like 2" and some change. The guys at Scat suggested a 7" rod, but for the street that would be counterproductive I think. This thing made 425 lbs of torque at like 3400.

 

I'm not familiar with the engine that you are building. Can you send the crankshaft to a grinder and have the rod journals widened to fit an off-the-shelf rod? Then get some good aftermarket rods and order your custom Pistons with the compression height set accordingly.

 

I dunno. That might be easier Joel. It's basically a factory gm stroker sbc. Its a 4" bore and a 3-7/8 inch stroke. It had a 10.5:1 compression ratio. It had factory forged innerds and a pseudo windage tray.

 

. We would use 6 inch Olds rods in our small block Chevy's. The tech man had to pull the motor all the way down to find them[/QUOTE]
We used Elgin 6-1/8" that looked stock. You could not tell them from stock thru the pipe plug mandatory in the pan. I'm sure they use cameras today.. I use 8" rods in my 302 GMC6's. Long rods work, at least for us.

 

If you do go with the Pontiac rods You might look a chevy 383 with 5.7 rod Pistons 390 pistons are 1.56 compression height the Pontiac rods are .150 longer 1.56 - .150 = 1.41 the 383s are 1.43 compression height would require bushing the rods but forged pistons would off the shelf. With stock rods a 350 chevy piston is 1.565. I narrowed ford 300 rods to use in a SBC on a Bridgeport and fine tuned the side clearance on a belt sander.

 

As Rich Fox said any machine shop can do it. I'd do it on a surface grinder. Hemi Joe's way would work too.

 

Buick big block rods are narrower than the Pontiacs. And the Buicks are 6.605, they have same big end as the Pontiac but a 1" pin, but if you are going with custom pistons that shouldn't be an issue. People used to narrow the Pontiacs to run in the Buicks. Company named Molnar makes some Buick rods now, couple of different lengths. Just a thought.

 

I built a 390 cad a few years back, first set of Pistons the customer got were Badger,told him to get his money back as some were 12 thou bigger than others second set were from Kanters two broke at the top ring land at 1500 miles then got some made by Venolia, has done 30,000 miles now with no issues.